1. Field of the Invention
The present invention relates to a fuel tank system, and more particularly to operation control of a display device in a closed type fuel tank until a filler lid is opened.
2. Description of the Related Art
In a conventional fuel tank system, there is a technique for preventing release of a fuel evaporative emission formed by evaporation in a fuel tank into the atmosphere, in which a sealing valve (hereinafter referred to as a tank blocking valve), which is controlled so as to close the fuel tank, is provided in a path allowing the fuel tank to communicate with a canister. The tank blocking valve is opened at the time of filling so that the fuel evaporative emission is allowed to flow to the canister, thereby allowing the canister to absorb the fuel evaporative emission.
In such a fuel tank system, if the fuel tank is closed by the tank blocking valve, fuel in the fuel tank evaporates with a rise in outside air temperature, so that pressure in the fuel tank, or fuel tank internal pressure, may become high due to a fuel evaporative emission. In addition, if a lid of a fill opening of the fuel tank is opened for filling and the like in a state where the fuel tank internal pressure is high, there is a possibility of release of the fuel evaporative emission in the fuel tank into the atmosphere.
Thus, in order to prevent release of a fuel evaporative emission into the atmosphere at the time of filling, if a driver performs an operation of opening a filler lid, the operation is detected, and a sealing valve is opened before the filler lid is opened so that the fuel evaporative emission is allowed to flow to a canister to release pressure in the fuel tank in advance, thereby sufficiently reducing the fuel tank internal pressure before opening the filler lid.
Unfortunately, if the fuel tank internal pressure is high, it takes time to release the pressure in the fuel tank. As a result, it takes time until a filler lid is opened after a driver performs an opening operation with a lid switch, thereby giving discomfort to the driver.
Japanese Patent Laid-Open No. 2010-120535, for example, describes a fuel tank system in which pressure release time, which is the time until the fuel tank internal pressure becomes equivalent to atmospheric pressure, is calculated from the fuel tank internal pressure at the time of closing an opening/closing valve (hereinafter referred to as a tank blocking valve), and the pressure release time is indicated on a display device to notify a driver, thereby reducing discomfort given to the driver.
In this fuel tank system, the fuel tank internal pressure during closure of the tank blocking valve is detected by a pressure sensor, and the pressure release time is calculated on the basis of the fuel tank internal pressure detected by the pressure sensor, thereby indicating the pressure release time.
However, fuel always evaporates in the fuel tank and an evaporation amount of the fuel varies depending on temperature of the fuel. Thus, in a case where fuel has a high temperature and there is a large evaporation amount of the fuel, for example, even if indication on the display device reaches the pressure release time, the fuel tank internal pressure does not become equivalent to the atmospheric pressure due to a large evaporation amount, and the filler lid is not opened. As a result, there is a possibility of giving discomfort to a driver, and this is not preferable.